In the construction industry, it is often desirable to create voids in various types of concrete formations for several reasons. First, it is often desirable to create voids in a below grade concrete formation which is in contact with the ground so that after the concrete dries, and the box void deteriorates, there will be enough space for the ground to expand, referred to as soil upheaval, thereby preventing damage to the concrete formation. Secondly, it is sometimes desirable to create a void inside of a concrete pillar or column in order to allow room for internal plumbing, electrical conduit, etc., contained inside the column. Such practice does not impair the structural characteristics of the column, but can amount to a considerable savings in the amount of concrete used as well as protecting the items in the column. Finally, box voids can be used above grade between cement floor slabs for the purpose of reducing the amount of cement required for a particular application and to make the resulting slab lighter in case the floor needs to be raised by hydraulic jacks or otherwise.
The prior art contains several different types of inserts used to create voids in concrete formations. For example, U.S. Pat. No. 3,358,960 discloses a reinforcing insert made of corrugated paperboard which is positioned to form a void in a cast concrete structure. The patent shows a single piece of paperboard having numerous flanges, slots, and perforations so that the paperboard can be folded, but it requires numerous complex steps to form a desired shape. In U.S. Pat. No. 2,881,501 there is shown a box-form structure which is capable of receiving a honeycomb reinforcing structure in order to add internal strength to the box void. Generally, the box voids of the prior art are complicated to assemble if they are a single piece of material, or require inserts to be added after the box form is completed to increase the internal strength of the box form. Either type is generally difficult to assemble on site and is costly in terms of manhours.